Conventional EEG Research Articles

A case of frontal lobe epilepsy in which amplitude-integrated EEG combined with conventional EEG was useful for evaluating clusters of seizures

Accurate evaluation of status epilepticus or clusters of seizures in patients with epilepsy is a critical issue in epilepsy care units. Although the need for continuous electroencephalographic monitoring has been recognized, it has been difficult to evaluate the frequency of ictal changes in electroencephalography (EEG) data in real time. Amplitude-integrated EEG (aEEG) has been reported to be useful for neuromonitoring, particularly in newborn infants. However, few reports of the utility of aEEG in older children with epilepsy have been published. We employed aEEG in combination with conventional EEG in an 11-year old boy presenting with clusters of seizures and were able to accurately evaluate the frequency of seizures in real time. The combination of aEEG and conventional EEG may be a useful tool in both neonatal intensive care units and epilepsy care units.

A comparative study of different references for EEG default mode network: The use of the infinity reference

Objective The choice of electroencephalograph (EEG) reference is a critical issue for the study of brain activity. The present study addressed the use of the infinity reference obtained by the reference electrode standardisation technique (REST) in the study of EEG default mode network (DMN). Methods A total of 100 randomly positioned source configurations, each consisting of two dipoles with coherent waveforms, were adopted for simulating EEG networks. Dense (129-channel), eyes-closed EEG was recorded from 15 subjects. Simulated data with infinity as reference and the real data were re-referenced to reconstructed infinity (REST), their average (AR), linked mastoids (LM) and left mastoid (L) references. For simulated data, the effects of different references on coherence and network were investigated. For real data, spectral properties of seven conventional EEG frequency bands were first analysed and then DMN was constructed based on the coherence. Results The simulation showed that REST can exactly recover the true EEG network configuration. For real EEG data, significant differences among references were found for the power spectra, coherence and DMN configuration. Compared with REST, the long-distance connectivity between anterior and posterior areas was strengthened by AR, and the connectivity over posterior areas was destroyed when LM and L were employed. Moreover, all comparisons demonstrated frequency-dependent reference effects. Conclusions Non-neutral reference influences the power spectra, coherence as well as the network analysis. REST demonstrates its validity in data referencing, and meanwhile, AR is much closer to REST than the other references in terms of spectra and coherence. However, the DMN alters a great deal with AR. Significance The results underscore the importance of considering EEG reference effects in the functional connectivity studies. REST is a promising reference technique for objective comparison in cross-laboratory studies and clinical practices.

Non-ketotic hyperglycinemia as a cause for respiratory failure in a newborn

Background: Non-ketotic hyperhyperglycinemia with manifestation in the neonatal period constitutes a severe inborn error of metabolism with a very poor prognosis. Methods: Case report Patient: The female baby was born to a GII, PI mother (unrelated parents) after an uneventful pregnancy with normal fetal movements (birth weight: 3510 gr) at 38 weeks of gestation. APGAR scores were 9 and 10at 5 and 10 minutes respectively. Mean blood pressure, heart rate, respiratory rate and core body temperature were normal. On day two of life the newborn had a poor suck and developed progressive lethargy. On physical examination generalized muscular hypotonia, absent deep tendon reflexes, extreme sleepiness, and insufficient respiratory drive were noted, which required mechanical ventilation. Serum chemistry, blood glucose, serum lactate and ammonia, and full blood count were normal. The recording of an amplitude-integrated EEG showed continuous burst suppression pattern despite administration of phenobarbitone and vitamin B 6. This finding was confirmed by conventional EEG recording (Figure 2). However, the neonate did not have manifest seizures. Further diagnostic work-up in our neonate for inborn errors of metabolism yielded the diagnosis of non-ketotic hyperglycinemia (glycine in CSF: 360.1µmol/l, reference value: 5.9–8.5µmol/l; plasma glycine: 2196µmol/l; reference value: 224–514µmol/l). After counseling the parents about the extreme poor prognosis that carries non-ketotic hyperglycinemia, intensive care treatment was withheld and the newborn was given palliative care. Conclusion: Inborn errors of metabolism (non-ketotic hyperglycinemia) have to be taken into the differenzial diagnosis of the severely floppy infant with respiratory insufficiency. Elevated glycin levels may cause peripheral floppiness with concomitant cerebral hyperexcitation.

An Easy and Practical Method for Routine, Bedside Testing of Somatosensory Systems in Extremely Low Birth Weight Infants

This study was set out to develop and describe a novel, simple, and safe method for routine bedside testing of somatosensory system in very early preterm infants. We recorded electroencephalogram (EEG) activity after tactile stimulation of hand (palm) and foot (sole) by a soft hairbrush stimulator in extremely low birth weight infants (n = 10; GA, 24-28, recording at conceptional age 30-32 wk) and compared with the raw EEG responses to those seen by one- or two-channel brain monitors. In every subject, single tactile stimuli produced prominent (100-350 microV) somatosensory evoked responses (SERs) that were readily identified in the ongoing EEG signal. The maximal SER was in the contralateral hemisphere at around the corresponding somatosensory representation areas. Conventional EEG filtering did significantly reduce the SERs, but they could still be identified in the routine brain monitor setting widely available in NICUs. The method described here is directly applicable to assessment of integrity of somatosensory system in the early preterm period. It needs minimal training and requires an EEG system or a brain monitor device that is available in most units. Thus, the technique is likely to open a novel window to neurologic assessment of these babies.

Amplitude-Integrated Electroencephalography in Neonates

Conventional electroencephalography (EEG) has been used for decades in the neonatal intensive care unit for formulating neurologic prognoses, demonstrating brain functional state and degree of maturation, revealing cerebral lesions, and identifying the presence and number of electrographic seizures. However, both the immediate availability of conventional EEG and the expertise with which it is interpreted are variable. Amplitude-integrated EEG provides simplified monitoring of cerebral function, and is rapidly gaining popularity among neonatologists, with growing use in bedside decision making and inclusion criteria for randomized clinical studies. Nonetheless, child neurologists and neurophysiologists remain cautious about relying solely on this tool and prefer interpreting conventional EEG. The present review examines the technical aspects of generating, recording, and interpreting amplitude-integrated EEG and contrasts this approach with conventional EEG. Finally, several proposed amplitude-integrated EEG classification schemes are reviewed. A clear understanding of this emerging technology of measuring brain health in the premature or sick neonate is critical in modern care of the newborn infant.

Sleep Spindle Activity Is Correlated With Reading Abilities in Developmental Dyslexia

To analyze sleep architecture of children with dyslexia, by means of conventional parameters and EEG spectral analysis and to correlate sleep parameters and EEG spectra with neuropsychological measures. Cross-sectional study involving validated sleep questionnaires, neuropsychological scales, and polysomnographic recordings. Sleep laboratory in academic center. Sixteen subjects with developmental dyslexia (mean age 10.8 years) and 11 normally reading children (mean age 10.1 years). All the subjects underwent overnight polysomnographic recording; EEG power spectra were computed from the Cz derivation and spindle density was calculated during sleep stages N2. N/A. Dyslexic children showed an increase in power of frequency bands between 0.5-3 Hz and 11-12 Hz in stage N2 and between 0.5-1 Hz in stage N3; they also showed significantly increased spindle density during N2. The power of the sigma band in N2 was positively correlated with the Word reading and MT reading tests; similarly, spindle density was significantly correlated with the Word reading test. The increased spindle activity and EEG sigma power in dyslexic subjects were found to be correlated with the degree of dyslexic impairment. The correlation found between sleep spindle activity and reading abilities in developmental dyslexia supports the hypothesis of a role for NREM sleep and spindles in sleep-related neurocognitive processing.

Detection of Ischemic Electroencephalography Changes During Carotid Endarterectomy Using Synchronization Likelihood Analysis

The intensive care unit is short of a suitable tool for instant detection of cerebral ischemia. Synchronization likelihood (SL) electroencephalography (EEG) analysis has proven to be a promising approach for instant online seizure detection. The aim of this study was to investigate the value of SL analysis in the detection of cerebral ischemia. SL analysis was studied using conventional EEG recordings during 143 carotid endarterectomy procedures. We compared EEG data before and after clamping of the carotid artery for 2 different anesthesia protocols (isoflurane or propofol) in patients with and without development of cerebral ischemia, making use of SL analysis. Cerebral ischemia was defined by using EEG variables. Fifty-eight patients received isoflurane and 85 propofol anesthesia of whom overall 27% developed ischemia. In patients from the isoflurane group who developed ischemia, the mean overall SL decreased [from 0.220 (SD 0.052) before clamping to 0.208 (SD 0.044) after clamping; P=0.06] In patients with ischemia in the propofol group, the mean overall SL remained stable (0.185; P=0.87) Patients from both groups without development of ischemia had increased mean overall SL values after clamping [isoflurane: from 0.210 (SD 0.041) before clamping to 0.219 (SD 0.051) after clamping; P=0.08. Propofol: from 0.188 (SD 0.019) to 0.189 (SD 0.021); P=0.57]. No significant changes in the mean SL were observed after development of ischemia during either isoflurane or propofol anesthesia. SL analysis does not seem suitable for detection of cerebral ischemia in anesthetized patients.

Abnormal auditory cortex with giant N100m signal in patients with autosomal dominant lateral temporal lobe epilepsy

Lateralization of functionally abnormal cortical area in autosomal dominant lateral temporal lobe epilepsy (ADLTE). A sound pulse of pure tone was delivered monaurally to the ears alternately. Auditory evoked magnetic fields (AEF) were measured by using whole-head magnetoencephalography (MEG) system. Significantly large N100m signals (a magnetic counterpart of N1/N100 in EEG) were detected in three out of five patients, either in the left or in the right hemisphere, contralateral to the auditory stimulation. The peak latency, location and orientation of distinct N100m exhibited no clear difference from those of normal controls. Unilateral cortical abnormality exists in some of the patients in ADLTE. Patients with abnormally large N100m had seizures apparently provoked by auditory stimuli, suggesting that the appearance of significantly large N100m is associated with the epileptogenicity. Based on the detailed examination using MRI and FDG-PET for two of the patients, the authors hypothesize hyperexcitability caused by the decreased inhibitory functions, larger number of synchronously activated neurons, or the elongation of neuronal firing in the pathological temporal cortex in ADLTE. The present study revealed clear abnormalities in the auditory cortex that have not been well detected by conventional EEG in patients with ADLTE.

Detection of subclinical electroencephalographic seizure patterns with multichannel amplitude-integrated EEG in full-term neonates

To compare the seizure pattern detection rate of single-channel and multichannel amplitude-integrated EEG (aEEG), using conventional EEG (cEEG) as a gold standard, in full-term neonates with hypoxic-ischemic encephalopathy. The optimal electrode derivation for seizure detection with single-channel aEEG was also investigated. Twelve infants with cEEG seizure patterns (10s) were investigated. cEEG signals were transformed into aEEG signals. Seizure patterns and the number of patients identified with 1 seizure patterns were calculated for single- and multichannel aEEG. On cEEG, 121 seizure patterns with a mean duration of 58s were identified, 68% of which occurred over the centrotemporal region. The sensitivity of aEEG for the detection of seizure patterns was 30% (C.I.: 0.22-0.38) for single-channel aEEG and 39% (C.I.: 0.31-0.48) for multichannel aEEG. Multichannel aEEG identified all patients with 1 seizure pattern (C.I.: 0.75-1.00), whereas single-channel aEEG (with C4-C3 as the optimal electrode derivation) identified all but one of the patients (C.I.: 0.66-0.99). Seizure pattern detection rate is slightly better with multichannel aEEG compared with single-channel (C4-C3) aEEG. Multichannel aEEG identified correctly all patients with 1 seizure pattern in this small selection of patients. Single-channel aEEG may detect most patients (in a selected group) with severe neonatal seizures patterns; patient identification can be improved using multichannel recordings.

Source Analysis of Alpha Rhythm Reactivity Using LORETA Imaging with 64-Channel EEG and Individual MRI

Conventional EEG and quantitative EEG visual stimuli (close-open eyes) reactivity analysis have shown their usefulness in clinical practice; however studies at the level of EEG generators are limited. The focus of the study was visual reactivity of cortical resources in healthy subjects and in a stroke patient. The 64 channel EEG and T1 magnetic resonance imaging (MRI) studies were obtained from 32 healthy subjects and a middle cerebral artery stroke patient. Low Resolution Electromagnetic Tomography (LORETA) was used to estimate EEG sources for both close eyes (CE) vs. open eyes (OE) conditions using individual MRI. The t-test was performed between source spectra of the two conditions. Thresholds for statistically significant t values were estimated by the local false discovery rate (lfdr) method. The Z transform was used to quantify the differences in cortical reactivity between the patient and healthy subjects. Closed-open eyes alpha reactivity sources were found mainly in posterior regions (occipito-parietal zones), extended in some cases to anterior and thalamic regions. Significant cortical reactivity sources were found in frequencies different from alpha (lower t-values). Significant changes at EEG reactivity sources were evident in the damaged brain hemisphere. Reactivity changes were also found in the "healthy" hemisphere when compared with the normal population. In conclusion, our study of brain sources of EEG alpha reactivity provides information that is not evident in the usual topographic analysis.

Statistical recognition pattern of EEG in diagnosis of Alzheimer's disease

Alzheimer's Disease (AD) is a cortical dementia and is therefore well suited for a technique like Electroencephalography (EEG) which measures the cortical activity of the brain. The main EEG abnormalities in AD are slowed mean frequency and reduced coherence among cortical regions. The diagnostic accuracy of conventional EEG in AD is around 80%. Statistical Pattern Recognition (SPR) is a statistical analysis that uses a database of information, in this case features from EEG registration, to identify individuals with aberrant pattern of brain waves. By using this method, the intention is to increase the diagnostic accuracy of EEG in AD. The participants were 300 patients diagnosed with AD at a Memory Clinic and 400 normal individuals evenly distributed in the age range of 50 - 90 years. SPR was used to identify the patients using more than 600 features of the EEG registration. A numeric index from 0-100 was established to describe the likelihood of AD in each case. This method correctly identified AD patients when compared to the normal group with >90% accuracy. Furthermore, the AD-index correlated with the severity of the disease as evaluated by the MMSE. The method also correctly identified AD patients when compared to EEG in patients with vascular dementia (VD) with some overlap in patients with mixed VD and AD. By using SPR on features of EEG registration, this method is more sensitive in identifying patients with AD from normal individuals and from patients with VD than conventional EEG. The method is easy to use and is therefore more widely applicable than more specialized methods like MRI or SPECT/PET.

Ictal Localization by Invasive Recording of Infraslow Activity with DC-Coupled Amplifiers

Scalp recording of infraslow (<0.5 Hz) ictal activity is useful for localizing partial seizures (Vanhatalo et al., Neurology 2003a;60:1198-1104, Miller et al., Neuroimage. 2007;35:583-597). This study further characterizes these infraslow ictal shifts with invasive recordings. Invasive monitoring captured 82 seizures in 11 patients with a 64-channel direct-current amplifier coupled to arrays of subdural platinum electrodes with bandwidth of 0 to 100 Hz. Time of onset, location, amplitude, duration, and polarity of infraslow signals were determined. Infraslow ictal signals (800-10,000 microV), were seen in 10 patients, starting from 2 seconds before to 493 seconds after electrical ictal onset time on conventional recording. Seven patients had an infraslow ictal signal in at least one channel localizing ictal onset on conventional recordings. Nine patients had surgical resections, including five with infraslow localizations concordant with conventional EEG (five had Engel class IA outcome, 1 class IB, 1 class IIIA, and one with no follow-up). Seizure localization using infraslow ictal activity was concordant with conventional EEG for most patients and is useful for confirming localization. The high voltage of infraslow activity may explain why infraslow activity localizes seizures better than conventional EEG with scalp recordings.

High-Density Transcranial Direct Current Stimulation (HD-tDCS): Hardware Interface

Transcranial Direct Current Stimulation (tDCS) is a non-invasive procedure where a weak electrical current (260 μA to 2 mA) is applied across the scalp to modulate brain function. tDCS has been applied for therapeutic purposes (e.g., addiction, depression, mood and sleep disorders) as well as cognitive performance enhancement (e.g., memory consolidation, motor learning, language recall). Despite safety and cost advantages, the developments of tDCS therapies have been restricted by spatial targeting concerns using existing two-channel systems. We have developed novel technology for High-Density tDCS (HD-tDCS) that improves spatial focality. Our hardware interface integrates a multichannel stimulating guide with existing two channel tDCS stimulators, and can be configured to target specific brain regions using computational models of current flow and multichannel array accessories. The hardware interface provides real time stimulation quality and safety feedback, and is designed to be MRI and TMS compatible. An electrical “tickle” feature enables skin pre-conditioning to minimize sensation. The full system includes the hardware interface, cable assemblies, head gear, tDCS electrodes, tDCS gel, and electrode adaptors. The head gear allows fixing the electrode adaptors over cortical targets using conventional EEG electrode coordinates. The electrode adaptors “fin” design, tDCS gel composition, and electrode shape are optimized to reduce sensation during direct current stimulation with 2 mA for up to 22 minutes. A five electrode system (4×1-C1), for implementing optimally focal “4×1 ring configuration” protocols, and an 8 electrode system (4×4-S1), that can be configured for “4×4 cortical strip stimulation”, are available. The entire system is robust, intuitive, and ultimately adaptable for home use. Our HD-tDCS system allows non-invasive, safe, and targeted modulation of selected cortical structures for electrotherapies that are individualized as well as optimized for a range of therapeutic applications.

14. Efficacy and limitation of the conventional neonatal EEG for extremely low birth weight infants

ignored the other three stimuli. The one of the three NoGo stimuli is visually most similar to the Go stimulus (similar condition), and another is most distinct from it (distinct condition). We obtained ERPs of the Go and NoGo conditions from 13-channel EEG recordings and measured peak latency, amplitude, and topographic distribution of the NoGo-N2 and NoGo-P3 components. Commission error was highest for the NoGo stimulus of the similar condition. The amplitude of NoGo-P3 was largest and the latency shortest in the distinct condition. The amplitude of NoGo-N2 was highest and distributed in relatively anterior regions in the similar condition. These results suggested that the conflict condition with visual difficulty of tasks may activate anterior cingulate cortex and prefrontal cortex.

Seizure Onset Determination

Digital electroencephalography has greatly expanded the opportunities for data analysis. Although commercial software packages are available they seem not to be used as widely in the preoperative work-up of epilepsy patients as might be warranted. This review will demonstrate that seizure onset can be better defined by judicious use of post hoc filter settings, expanded electrode coverage, and special electrode montages. In scalp recordings, ictal baseline shifts and infraslow activity (ISA) can be evaluated with conventional EEG systems by opening the high-pass filter to 0.01 Hz; in intracranial recordings high-frequency activity (>60 Hz; HFA) can be observed in addition. Inasmuch as ISA and HFA have considerably smaller electrical fields than the conventional frequencies they may better define seizure onset than might be possible otherwise. It is recommended that to determine the clinical value of ISA and HFA for epilepsy surgery, retrospective analyses of seizure data, which include assessment of ISA and HFA, be performed from patients who have undergone surgical resections of epileptogenic tissue. These may yield information as to whether or not the epileptogenic areas of ISA and HFA had been included in the resected tissue and their relationship to surgical outcome can then be determined.

Limitations of single-channel EEG on the forehead for neonatal seizure detection

In amplitude-integrated EEG, lead placement across the forehead is convenient, but this location has unknown effects on neonatal seizure (NS) detection sensitivity. This study describes the limits of NS detection by a single forehead EEG channel. Records were taken from a digital library of conventional EEGs (CEEGs) with NS, previously characterized at a bicentral channel, C(3) --> C(4). We analyzed electrographic characteristics in a single forehead channel, Fp(3) --> Fp(4). A total of 330 seizures from 125 CEEGs were included. With Fp(3) --> Fp(4), at least one NS was detected in 66% of records vs 90% using C(3) --> C(4) (P<0.0001). Of 330 seizures, 46% appeared in Fp(3) --> Fp(4) vs 73% in C(3) --> C(4) (P<0.0001). Seizures appeared briefer in Fp(3) --> Fp(4) than C(3) --> C(4) (P<0.006) and CEEG (P<0.0001). NSs are significantly more difficult to detect with a single forehead channel than bicentrally or on CEEG. In Fp(3) --> Fp(4), a third of records with seizures were missed and over half of seizures were undetected.

Amplitude-Integrated Electroencephalography in the Newborn: A Valuable Tool

The use of amplitude-integrated electroencephalography (aEEG) for research and clinical use in the newborn infant has increased over the last 2 decades. However, with this increased use, concerns have been expressed about (1) the accuracy and reliability of the interpretation of aEEG by neonatal clinicians and (2) the lack of evidence of benefit from aEEG monitoring for the infant.1 As early as 1994, Greisen2 noted that lack of knowledge of whether and when to act on the information obtained with aEEG, rather than the technology itself, limited the usefulness of this technique in the newborn. The aims of this commentary are to address these concerns by first reviewing the historical context in which the aEEG was developed and then summarizing current evidence on the use of aEEG in the newborn. aEEG is not a new technology. The cerebral function monitor (CFM) was devised by Dr Douglas Maynard and its clinical potential was explored by Dr Pamela Prior in the 1960s as a means of monitoring cerebral function in adults undergoing bypass surgery and after resuscitation.3,4 With its time-compressed output, the CFM provided a simpler and cheaper means of following trends in cerebral function in the ICU and the operating room without the need for experienced technicians for application, voluminous recordings, and expertise in interpretation for the, then, analog conventional EEG systems. The electrode placement over the parietal areas (P3–P4 in the 10–20 system) was designed so as to be in close proximity to the vulnerable “watershed” regions of the brain in the border zones of arterial blood supply from all 3 cerebral arteries. This position also minimized artifacts from sweating, muscle activity, and eyelid … Address correspondence to Divyen K. Shah, MB, ChB, Washington University, Department of Pediatrics, 8th Floor, NW Tower, 1 Children's Place, St Louis, MO 63110. E-mail: shah_d{at}kids.wustl.edu

The value of video-EEG monitoring to diagnose juvenile myoclonic epilepsy

Objective A diagnostic accuracy of conventional electroencephalography (EEG) is approximately 50% at best. We aimed to determine the accuracy of video-EEG monitoring (VEM) for a correct diagnosis and the feasibility of its clinical application. The data from all 55 patients (M:F = 31:24) with juvenile myoclonic epilepsy (JME) who underwent VEM were reviewed according to the clinical history, brain imaging and video-EEG findings. Results Age at seizure onset ranged from 10 to 25 (15.5 ± 2.7 years). The age at VEM ranged from 15 to 46 (21.8 ± 5.8 years) and 57% (29/51) showed seizures. Of those, 20 patients (69%) showed myoclonic jerks alone, whereas 3 (10%) showed generalized seizures alone. Both of these conditions were observed in 6 patients (21%). Interictal abnormalities alone without clinical seizures were detected in 16 patients (31%). Atypical semiologies such as asymmetric myoclonus or versive seizures were observed in 18 patients (35%) during video monitoring. Interestingly three patients complained of visual aura on history. The duration of VEM ranged from 1 to 6 days (1.8 ± 1.1). Overall, 88% of patients showed an EEG abnormality with/without seizure, concordant with JME. Among 10 patients with a normal conventional EEG before VEM, 9 showed interictal or ictal EEG abnormalities during approximately 1-day of VEM. Conclusions VEM for 1 or 2 days is appropriate for making a correct diagnosis of JME, especially in patients having an atypical semiology and a normal result on the conventional EEG.

Electroencephalographic Cerebral Dysrhythmic Abnormalities in the Trinity of Nonepileptic General Population, Neuropsychiatric, and Neurobehavioral Disorders

Electroencephalographic Cerebral Dysrhythmic Abnormalities in the Trinity of Nonepileptic General Population, Neuropsychiatric, and Neurobehavioral Disorders

Electroencephalographic Cerebral Dysrhythmic Abnormalities in the Trinity of Nonepileptic General Population, Neuropsychiatric, and Neurobehavioral Disorders

Subclinical electroencephalographic epileptiform discharges in neurobehavioral disorders are not uncommon. The clinical significance and behavioral, diagnostic, and therapeutic implications of this EEG cerebral dysrhythmia have not been fully examined. Currently the only connotation for distinctive epileptiform electroencephalographic patterns is epileptic seizures. Given the prevailing dogma of not treating EEGs, these potential aberrations are either disregarded as irrelevant or are misattributed to indicate epilepsy. This article reappraises the literature on paroxysmal EEG dysrhythmia in normative studies of the "healthy" nonepileptic general populations, neuropsychiatry, and in neurobehavioral disorders. These EEG aberrations may be reflective of underlying morpho-functional brain abnormalities that underpin various neurobehavioral disturbances.